Although it can be applied to any desired fibre composite components, the present invention and the problems on which it is based are explained in more detail below with reference to two-dimensional stringer-stiffened carbon fibre reinforced plastic (CRP) components, for example skin shells of an aircraft.
It is state of the art to stiffen CRP skin shells with CRP stringers in order to withstand the loads occurring in aircraft construction with the lowest possible additional weight. In this respect, a distinction is made essentially between two types of stringers: T and Ω stringers.
The cross section of T stringers is made up of the base and the stem. The base forms the connecting surface with respect to the skin shell. The use of skin shells stiffened with T stringers is widespread in aircraft construction.
Ω stringers have something like a hat profile, its ends being connected to the skin shell. Ω stringers may either be adhesively attached in the cured state to the likewise cured shell, or be cured wet-in-wet at the same time as the shell. The latter is desired, because it is more favourable from technical aspects of the process. However, supporting or moulding cores are necessary for the wet-in-wet production of skin shells stiffened with Ω stringers, in order to fix and support the dimensionally unstable semifinished fibre products in the desired Ω shape during the production process. Skin shells with Ω stringers have the advantage over T stringers that they allow better infiltration during an infusion process for introducing a matrix, for example an epoxy resin, into the semifinished fibre products. Infusion processes may be inexpensive in comparison with other known methods for producing fibre composite components, such as the prepreg process for example, because they allow the use of lower-cost semifinished fibre products.
However, there is the problem with the production of Q stringers that, when they are applied and/or removed after the forming of the Ω stringers, certain supporting or moulding cores have to be subjected to a medium which on the one hand makes it possible or easier to help them to retain their shape when they are applied and on the other hand makes it possible or easier to remove them. Therefore, such moulding cores are accordingly connected with preference to a medium source.
The document GB 2 292 332 A describes a moulding method and a device with which an elastomer mould bag is arranged in a mould. The elastomer mould bag is connected by its inlet to a connection, a closure cap, of a vent line and to a valve. The mould also has a vacuum channel.
The document U.S. Pat. No. 4,389,367 describes a fluid moulding system for producing moulding cores for moulded components. When a component is produced with the moulding cores, the moulding cores are connected to a vacuum source by means of plugs and lines.